Antoni isn't important enough to be invited to stay at anyone else's manor, nor even to be invited to their dinner parties. But he's still a nobleman, and it would be beneath his dignity to try to save money on lodgings by renting something in an inexpensive neighborhood. He's rented out a set of rooms in a mansion in the expensive part of Westcrown.

This is, of course, exactly where the mob is gathering. The parts of it that listened to the pamphlet with Valia Wain's speech, anyway, not the parts that are just going after people they don't like. (Antoni doesn't, technically, have proof that there's anyone doing that, but he doesn't need to have seen it happen for it to be obvious.)